Lead screw assemblies are well known devices for linearly actuating devices. A lead screw assembly uses rotational motion of a lead screw to linearly actuate a nut having internal threads that engage the external threads of the lead screw. Rotation of the screw in a first rotational direction actuates the nut in a first linear direction along the axis of the screw and reversing rotation of the screw to a second rotational direction actuates the nut in a second linear direction, opposite the first linear direction, along the axis of the screw. As such, the nut is mounted for rectilinear motion along the lead screw.
Prior lead screw assemblies are known, for example, U.S. Pat. No. 5,913,940 to Erikson et al., RE 32,433 to Erikson et al., and U.S. Pat. No. 8,028,594 to Schroeder and assigned to the assignee of the instant application illustrate lead screw assemblies that include nuts that have flexible fingers to permit adjustment or predetermined biasing of the threads of the nut towards and against the threads of the lead screw.
One problem with prior art nuts with flexible fingers is that they use an axial force to bias an inclined ramp against a rib or projection on the outer surface of the flexible fingers. The interaction of the ramp and rib/projection transform the axial force into a radially directed force. Unfortunately, to create sufficient radial force, the ramp angle must be relatively large. This creates an interface between the inclined ramp and the projection that experiences significant stick slip. The stick slip reduces the functionality of the device limiting the ability for infinite compensation.
The present invention is directed toward improvements in relation to the lead screw and nut interaction of lead screw assemblies.